STABILITY OF THE MESSENGER-RNA ENCODING SOME PANCREATIC HYDROLASES ISMODULATED BY DIETARY-PROTEIN INTAKE IN THE RAT

Wistar rats fed on either a high-protein or a protein-free diet were e xamined to determine their pancreatic hydrolase mRNA stabilities in co mparison with those of control animals receiving a standard diet. Acti nomycin D was used to inhibit transcription and, after isolating the p ancreatic RNA, the specific messengers were quantified by performing d ot-blot hybridization with cDNA probes. In the rats fed on a high-prot ein diet, only the half-lives of anionic trypsinogen I and elastase I( EC 3.4.21.36) were affected. Interestingly, when rats mere fed on the protein-free diet, most of the hydrolase mRNA half-lives showed change s, except that corresponding to lipase. In these rats, the half-hfe va lues of the mRNA coding for anionic trypsinogen I, chymotrypsinogen an d procarboxypeptidase B increased, in sharp contrast with those of the amylase and elastase I mRNA, which decreased. These results strongly suggest that the mechanism whereby the biosynthesis of pancreatic hydr olases is regulated, depending on the presence or absence of proteins in the diet, is not unique and provide evidence that the stability of mRNA encoding most, if not all, the hydrolases in pancreatic cells is modulated by the dietary protein content.